Study On Capillary Driving And Heat Transfer Performance Of Micro Heat Pipe Based On Different Channels

With the continuous development of social productivity,people are increasingly pursuing the high efficiency of products.Especially for micro-electronic products,the cooling effect of the internal micro-heat pipe is related to the performance of the micro-electronic products.Therefore,how to enhance the capillary reflux force,improve the heat transfer ability of the existing micro heat pipe,and play the best heat transfer performance of the micro heat pipe is the key to study.In this paper,the capillary driving force and heat transfer performance of rectangular groove micro heat pipe were studied.First,the heat transfer limit of rectangular groove micro heat pipe was analyzed,and the relationship between the width of groove,the number of groove and the ratio of depth to width and the capillary limit was explored with Matlab graphic analysis.Secondly,the micro-heat pipe grooves with different structural sizes were processed on the aluminum substrate,and the platform for vacuuming and pouring working medium of the micro-heat pipe was built.The sealing,liquid filling and leak detection methods of the micro-heat pipe were designed.Finally,a heat transfer performance test platform is built,which includes a designed and processed micro heat pipe fixation and Angle adjustment device.The inclination can be adjusted and fixed within the range of 0～90°,and the minimum adjustable Angle is 1°.In the process of experiment,14 kinds of micro-heat pipes with different structural scales were designed in this paper.The slot width specifications were 0.4 and 0.6mm,the number of slot channels was 17 and 26,and the ratio of depth to width was 1.1,1.8,2.6 and 3.9,and they were numbered respectively.Three kinds of liquid working medium acetone,cyclopentane and ethanol were selected as the working medium of the micro-heat pipe.The capillary rising height of several kinds of micro-heat tubes with different rectangular section sizes was measured.The results of dynamic height method and capillary force characterization showed that the most obvious capillary rising phenomenon was acetone,followed by cyclopentane and ethanol.The results show that acetone has the best wetting effect on aluminum plate.The larger the depth-width ratio of the rectangular groove,the greater the capillary force value,because the deeper the micro-heat pipe groove,the stronger the capillary force.Finally,the optimal channel structure and the optimal liquid filling medium of micro heat pipe are selected.At the same time,the surface of the micro heat pipe was modified by nitrogen and argon plasma to enhance the wettability of the working medium.The dynamic height of the modified surface showed that the surface of the micro heat pipe was modified by plasma to improve the capillary force.The heat transfer test results of the above 14 kinds of micro heat pipes show that the heat transfer performance of micro heat pipes with large channel aspect ratio is better,but the heat transfer effect will be weakened to a certain extent if the depth aspect ratio is too large.The influences of channel section width and channel number on the heat transfer effect are inconsistent.In this paper,the 26 channel heat transfer effect of the micro heat pipe with smaller channel section width is better,while the 17 channel heat transfer effect of the micro heat pipe with larger channel section width is better.The modified surface nitrogen can also improve the heat transfer effect,and the equivalent thermal conductivity of the microheat pipe is increased by about 11.38% compared with that of the groove surface.The test data show that the micro-heat pipes designed and machined in this paper can be started successfully and maintain a certain temperature uniformity on the surface of the heat pipe.